1. Technical Field
The present disclosure relates to a transverse connector for interconnecting a first and a second rod, which are in an approximately parallel relationship to each other. More particularly, the present disclosure relates to an offset transverse connector having opposing ends and being capable of independent multidirectional articulation while preserving space for the anatomy.
2. Background Art
Disease, the effects of aging, or physical trauma resulting in damage to the spine has been treated in many instances by fixation or stabilization of the effected vertebra. A wide variety of spinal fixation apparatuses have been employed in surgical procedures for correcting spinal injuries and the effects of spinal diseases. For example, as illustrated in FIG. 16, many of these apparatuses commonly use a pair of longitudinal rods 50 running in a relatively parallel relationship to each other and the spinal column S to correct any spinal deformity involving a convexity or a concavity. These rods 50 are connected to coupling elements, which in turn are secured to the underlying vertebral bone V by spinal bone fixation fasteners such as pedicle screws, hooks, and the like. More particularly, depending upon the nature of the deformity, suitable bone screws 48 may be first implanted into the vertebral bone V of the spinal column S at multiple points above and below the apex A of the curve. Rod reduction devices 10 including manipulation devices 28 adapted and configured for attachment to heads of the bone screws 48, and which provide leverage to facilitate the manipulation of the spinal column S, can then be attached to the heads of the bone screws 48. With continuing reference to FIG. 16, the rod reduction device 10 is attached to the heads of the bone screws 48 on the concave side S1 of the spinal deformity. The manipulator device 28 is placed on the bone screws 48 on the convex side S2 of the spinal deformity. Depending upon the nature of the deformity, the rod reduction device 10 can be used on both sides of the deformity.
Prior to any correction of the rods 50, the surgeon can manipulate and correct the curve of the spinal column S to a large degree. That is, the surgeon can first manually manipulate and reduce the “rib hump.” The spinal rod 50 can be pre-bent to the configuration of the normal spinal curve, e.g., the sagittal curve. Once certain the spine S is in the proper anatomical position, the surgeon can position the pre-bent spinal rods 50 relative to the screws 48 and the rod reduction devices 10, and lock each rod 50 to the first two points of the spinal column where the construct is to be attached for enabling the correction of the deformity. In order to facilitate the desired positioning of the pair of longitudinal rods 50 relative to the spinal column S, the pair of longitudinal rods 50 can be held in position relative to one another by transverse connectors, also known as transverse bridge elements or cross-connectors.
As the technology of spinal surgery has developed and improved, each of the spinal fixation components has also undergone improvements and modifications to address the shortcomings of conventional spinal appliances. The natural anatomical variations in the spinal column of a subject are such that implanted spinal rods while approximating a parallel relationship one to the other can vary from that parallel relationship considerably and in multiple planes. For this reason, any transverse connector used to attach the two rods to each other should not be of a rigid design without the ability to be re-configured as needed during the process of implanting and attaching to the two opposing rods. While some improvements have been made in the articulation and re-configuration operation of transverse connectors during the implantation and rod connecting process, a continuing need exists to provide a multidirectional articulating transverse connector that can adapt to a wide variance in the contours of the spinal column. Further, a need exists to provide such a transverse connector that can provide sufficient space for the underlying anatomy, most specifically, the dura and spinal cord, while still maintaining a low profile and a smooth contoured surface to thereby reduce the potentially negative impact of the implanted device on the underlying and surrounding soft tissue of the subject into which the device has been surgically implanted.
Conventional efforts to meet this need have fallen short of the desired transverse connector configuration. For example, U.S. Pat. No. 6,554,832, issued to Shluzas, as best seen in FIGS. 2 and 4 of that patent, provides a transverse connector, which includes first and second connector members for connecting to the respective first and second spinal rods. The two connector members are connected one to the other by a connecting rod, which can be withdrawn or extended in alignment with the longitudinal axis of the cross-connector for purpose of adjusting the length thereof. As shown in FIGS. 2 and 4 of the Shluzas patent, the articulation of the connecting members to align with the two opposing spinal rods is limited to a single, centrally disposed ball joint (50). Importantly, the pivoting movement of the Shluzas connector is limited to movement within the same horizontal plane relative to the longitudinal axis of the spinal column. Thus, while the device of Shluzas does permit some limited adjustment in length and azimuth of the device, it is configured to structurally prohibit any upward or downward movement in relation to the surface plane of the spinal column. That is, the elevation of one end of the Shluzas connector relative to the other end of the connector cannot be adjusted. Thus, while the Shluzas design does provide some flexibility in adapting the alignment of the transverse connector to the opposing spinal rods, it falls short of the greater degree of adaptability that could be obtained by a truly multi-planar transverse connector having multiple articulating points. In U.S. Pat. No. 6,110,173, issued to Thomas, more specifically FIGS. 1 and 3, show the rigid nature of the cross connecting rod which does not allow for sufficient space for spinal anatomy. In this regard, the current device affords an improvement in this area as well since the cross-connecting member is arched to allow for such anatomy.
For reasons discussed above a continuing need exists for a transverse connector that provides ease of operation by the surgeon to simultaneously adjust in multiple dimensions one spinal rod connecting end of the connector in relation to the other spinal rod connecting end of the connector and to provide a transverse connector having means for providing sufficient space for spinal anatomy and smooth contours for surfaces in contact with adjacent soft tissue.